1. Field of the Disclosure
This disclosure generally relates to a human machine interface device and, more particularly, to a displacement detection device and a power saving method thereof that may keep the average current consumption of the light source low and may maintain the image brightness as well.
2. Description of the Related Art
Traditionally, the optical mouse is served as one of the peripheral devices configured to interact with a computer system having a display screen. An optical mouse generally has a light source, an image sensor and a processing unit. The light source projects light to a work surface. The image sensor receives reflected light from the work surface and successively outputs image frames. The processing unit calculates a displacement of the optical mouse with respect to the work surface according to the image frames to accordingly control the computer system.
In order to improve the operational convenience of an optical mouse, the optical mouse can transfer the displacement information to the computer system via wireless transmission. Therefore, how to save the average consumption power of the optical mouse and to extend the service time of the battery becomes an important issue.
Referring to FIG. 1, it shows a schematic diagram of the image capturing and the emission of the light source in the conventional optical mouse. The image sensor successively captures image frames at a sampling frequency. When the optical mouse is moved at high speed, the light source is lighted at a high emission frequency whereas when the optical mouse is moved at low speed, the light source is lighted at a lower emission frequency so as to reduce the consumption current of the light source. However, in this power saving method the consumption current of the light source at high speed is still about twice of that at low speed.
Accordingly, the present disclosure further provides a displacement detection device and a power saving method thereof that may reduce the consumption current of the light source by changing both the emission frequency and the emission duration thereby reducing the total power consumption.